May 16, 2013

Researchers Develop Paper-Thin Heart Monitor Worn On The Skin

A team from Stanford University writing in the journal Nature Communications say they have developed a wearable heart monitor that is thinner than a dollar bill.

The engineers combined layers of flexible materials into pressure sensors to create the new skin-like heart monitor. They said their device could be used to continuously track heart health and provide doctors with a safer alternative when checking the vital signs for a newborn.

"The pulse is related to the condition of the artery and the condition of the heart," Zhenan Bao, a professor of chemical engineering at Stanford whose lab develops artificial skin-like materials, said in a statement. "The better the sensor, the better doctors can catch problems before they develop."

Each pulse beat is made up of two distance peaks, the first being your heart pumping out blood and the second being your lower body sending a reflecting wave back to your artery system. The sizes of these beats can be used by medical experts to measure heart health.

"You can use the ratio of the two peaks to determine the stiffness of the artery, for example," said Gregor Schwartz, a post-doctoral fellow and a physicist for the project. "If there is a change in the heart's condition, the wave pattern will change. Fortunately, when I tested this on myself, my heart looked fine."

The researchers used a thin middle layer of rubber to make the heart monitor both sensitive and small. They were not only able to make it thinner than a dollar bill, but the team also created it to be just a little wider than a postage stamp.

The device contains tiny pyramid bump sensors that are just a few microns across, which is smaller than a human red blood cell. When pressure is applied to the device these pyramids deform, causing a measurable change in the electromagnetic field and the current flow in the device. The more pressure applied to the monitor, the more the pyramids deform and the larger the change in electromagnetic field. This technique allows the device to detect more than just two peaks of a pulse, but the tiny heart monitor could potentially be used for detailed diagnostics in the future.

"In theory, this kind of sensor can be used to measure blood pressure," said Schwartz. "Once you have it calibrated, you can use the signal of your pulse to calculate your blood pressure."

The team is now working to try and make the device completely wireless, which would allow doctors to receive a patient's minute-by-minute heart status through a smartphone.

"For some patients with a potential heart disease, wearing a bandage would allow them to constantly measure their heart's condition," Bao said. "This could be done without interfering with their daily life at all, since it really just requires wearing a small bandage."